Short-range wireless technologies in the wireless local area network (WLAN) space as well as wireless personal and body area networks (WPAN and WBAN) continue to proliferate rapidly. Similarly, wireless technology is increasingly applied to feed high-resolution video signals over a digital video interface (DVI) to hand-held or detachable flat panel displays (FPDS) as well as to stationary displays, e.g., display panels mounted on a wall a missing feature in these applications using DVIs is the capability to support user-aware, real-time or quasi real-time interactions in response to the user's position and orientation relative to the video display. Typically, conventional wireless video display systems operate by transmitting compressed video signals to the display, such that the latter requires decompression circuits, over license-free but narrow designated radio spectrum bands; however, these narrowband wireless systems can generally not support the desired high data rates for the transmission of raw high-resolution video signals. Furthermore, narrowband wireless systems are generally not capable to support applications requiring a precise indoor location tracking capability.
To mitigate the threat of a future spectrum shortage, additional radio spectrum in the form of the ultra-wideband (UWB) radio channel was recently made available for use in the USA in the range 3.1 GHz-10.6 GHz. European and Asian authorities are also preparing rulings to enable commercial marketing and use of devices based on UWB radio technology (UWB-RT).
High-definition television (HDTV) and high-resolution video display rendering will use DVIs with the added disadvantage that high transmission data rates are to be used between the video signal source and the display. For example, the digital DVI (DVI-D) standard link allows a digital connection from a set-top box (STB) to a display eliminating unnecessary digital to analog conversions and keeping the signal digital. Almost all STBs use DVI-D and do not carry any analog signal. An HDTV capable TV set has maximum resolution of 1920×1080 pixels (60 Hz AC power supply) and should only use a single link (cable or wireless), as do almost all DVI equipped displays. However, plasma screens and flat panel displays (FPDs) can have much higher resolutions and refresh rates and could use a dual or multiple DVI-D links. The requirement for very high data rates between the video signal sources and high-resolution displays is particularly demanding if the video signal is to be transmitted wirelessly to the display. Thus, there is a need for new solutions to increase both the effective data rate and the link distance between the video source and the display. This problem prevails equally when connecting a personal computer (PC) to a high-resolution video display through DVIs or other digital interfaces.
One possibility to overcome this problem is to split a high-rate data stream into multiple lower-rate data streams to achieve a compound data rate equal to the desired high-data rate. In such cases, designers are faced with the problem of choosing the best possible multi-stream technology for a given set of system parameters and criteria. There exist two different approaches: a) support of multiple data streams by means of co-located and non-interfering networks, also called piconets, and b) support of multiple data streams within a single communication cell based on a suitable multiple access (MA) technique. All of these approaches are based on an efficient channel access method and the most popular prior art MA methods are briefly described hereafter, listing their known features and suitability when applied to networks with terminals based on UWB-RT.
MA techniques, e.g., Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Code Division Multiple Access (CDMA), and in particular Rate Division Multiple Access (RDMA) as described by Martin Weisenhorn and Walter Hirt, “Novel Rate-Division Multiple-Access Scheme for UWB-Radio-Based Sensor Networks”, IEEE Int. Zurich Seminar on Communications, pages 76-81, February 2004, have been known for some time. Some of these techniques could be applied to mitigate the high-rate video distribution problem. For example, when using RDMA, each data stream is transmitted by a binary antipodal signal, preferably with a low duty cycle, that can be distinguished at the destination receiver by an appropriate, unique choice of a user-specific pulse rate or a combination of at least two user-specific pulse rates. However, it may be advantageous in certain applications to combine the features and benefits of the basic RDMA method with one or more of the prior art multiple access methods.
Known wireless (video) displays include:                PDA-like screens of low pixel resolution (320×240), near/full-motion video (15/30 fps (frames per second)), in high or true color format (12, 16 or 24 bit/pixel);        tablet—SVGA up to XGA resolution, 16/24 bit/pixel, with full or reduced refresh rate; if full-motion video is supported, then the video stream is commonly MPEG-encoded when sent over a wireless channel, with data rates of 1-10 Mbps; and        video projectors and TV displays with internal MPEG decoding engine and Wi-Fi® capability with nominal data rates of 11-54 Mbps (Wi-Fi is a registered trademark of the Wi-Fi Alliance).        
While some of the above will support full-motion video in DVD or even HDTV quality, none of these display devices can sustain the high-resolution full-rate refresh requirements of a standard PC over a wireless channel. A distinction is made between a cinematographic and “full-motion” video display of 25, resp. 30 fps, and a more demanding notion of “full-rate” computer monitor, with refresh rates in excess of 60 fps. Here the requirements of full-rate display refresh are addressed.
A question worth asking is: How to wirelessly connect a full-rate high resolution PC monitor? A brief step-wise calculation of the bandwidth requirements yields the following results:                a) A typical PC monitor resolution ranges from XGA (1024×768) up to QUXGA-W (3840×2560); most common resolutions are SXGA/+(1280×1024) and UXGA (1600×1200). The large scale introduction of HDTV will drive the standard PC resolution up to QXGA (2048×1536).        b) The minimum refresh rate for PC displays in TFT LCD technology is 60 fps.        c) Unlike video codecs such as MPEG-2/4, there seem to be no general codecs for GUIs (Graphical User Interfaces). A universal GUI display that works with a common operating system uses the least common denominator, i.e., un-encoded video transmission between the computer video source and its display. Otherwise, the lack of a large enough market would not allow the widespread use of full rate/motion wireless displays.        
Thus the net bandwidth required by an XGA display at 60 fps is: (1024×768 pix)×(24 bit/pix)×(60 fps)=1132 Mbps or 1.132 Gbps. Assuming a 25% overhead for wireless encoding and protocol, the raw data rate for XGA is ˜1.4 Gbps; for QXGA: ˜5.7 Gbps; for QUXGA-W: ˜17.7 Gbps.
Considering SXGA/UXGA, the most likely resolution used for PC, notebook and HDTV flat screens, it is found that the raw data rates are also very high for wireless transmission (SXGA: ˜2.4 Gbps; UXGA: ˜3.5 Gbps).
From the above it follows that there is still a need in the art for a scheme that allows displaying of a video signal on a display without cables and in particular in dependence on a user interaction. It would be further advantageous if the scheme enables a user-aware wireless video display offering full rate refresh at high resolution.